Process for treating mineral oils



July 14, 1936. M. R. FENsKE ET Al. 2,047,363

PROCESS FOR TREATING MINERAL OILS Filed AprilylS. 1934 ma' *@Gm Patented `uly 14, 1936` aorzssa PROCESS non TREATING MINERAL ons Merrell n. renske and Wilbert B. Mcoiue'r, state' College, Pa., assig'nors to Pennsylvania Petroleum Research Corporation, a corporation of Pennsylvania Application api-ii i3, 193i, serial NaA 'nicnas e i5 claims. (cineisi This invention pertains generally to the sepa` ration oi mineral oils into components. It will be described in connection with the improvement of lubricating stocks of Pennsylvania grade.

However, it is to be understood that it may have other uses.

In-accorgdance with this invention crude petroleum or products thereof and particularly lubricating oils are separated into various components by treatment with benzyl acetate or a mixture containing benzyl acetate in sufficient quantity tobe eiective as such.

While we appreciate that practically nothing is known concerning denite substances which comprise the complicated mixture known as mineral oil and still less is known concerning the compounds present in the heavier or lubricating oil fractions except that the molecular weights of the molecules are large, which makes it possible to have varying types oi structure existing in the same molecule, yet there is evidence which leads to the conception that the types of molecules in lubricating oils may be divided into perhaps three classes. i 1

The molecules of these three classes'are thought to have structures containing rings and chains and the following hypothetical classification is based, first, upon whether the rings are unsaturated or saturated and second, upon the relative length of the chains attached to the rings. t

The term chain implies either substantially a straight chain or a relatively highly branched chain. V

The molecules of the first class are conceived to have rings which are appreciablyunsaturated (i. e. hydrogen may be added without appreciably changing the molecularl conguration) chains attached to the rings but with the ring type of structure preponderating. Molecules of` this class may be regarded as having asphaltic characteristics.

The molecules of the second class are conceived to have rings which Iare principally saturated,

such as those of cyclopentane or cycloherane,`

the rings. Molecule of this class may be regarded as having naphthenic characteristics.

With

The molecules of the third class are conceived f to have rings which are predominately saturated (i. e. the larger part oi the carbon atoms have associated with them as many other carbon and/or hydrogen atoms as possible without ap#- preciably changing the molecular structure) and to have chains attached to these rings which are relatively long and involved compared to the chains of the second class. The carbon atoms in the chains are thought to be materially in excess of those in the rings. This class of molecules may be regarded as having paraimlc characteristics.

y It is to be understood, however, that the foregoing thoughts relative to molecular arrangements are employed simply to portray the overall or average condition of the molecular species constituting an oil and that any one or more of such molecular arrangements may comprise petroleums or oils according to the type.

Oils of Pennsylvania grade are composed preponderately oi molecules of the third class.

Solvent extraction processes oi the prior art relate principally to the removal of molecules of Oils of Pennsylvania grade are universally re-s garded as premium lubricants and improvements in such oils by the process herein are due toa considerably dierent eect, and entirely separate and distinct problems are involved. i y Outstanding among these problems is the removal from lubricating oils of Pennsylvania grade of materials responsible for the relatively high Conradson carbon residue which is particularly characteristic of these o'ils. This problem is ol equal if not of greater importance than that of decreasing the rate of change of viscosity with temperature.

This problem is not of equal importance in the refining of lubricating oils derived from crudes emanating from oil iields outside of the Pennsylvania area. The absence of a relatively high Conradson carbon is substantially the only characteristic in which lubricating oils derived from crudes outside of the Pennsylvania area may be regarded as being of a quality comparable to Pennsylvania grade lubricating oils.

The rate of change of viscosity with temperature is at present largely measured in terms of the viscosity index as developed by-Dean and Davis (Chemical and Metallurgical Engineering 36,618 (1929) and revised by Davis, Lapeyrouse, and Dean (Oil Gas Journal, (46), 92 (1932)).

However, we have found that the viscosity index developed according to the foregoing is unsatisfactory and inaccurate for oils of lower viscosity than 55 Saybolt seconds at 210 F. Ilherefore, in developing the data hereinafter we have employed the conventional method for evaluating the viscosity index of oils more viscous than 55 Saybolt seconds at 210 F. but for oils of lower viscosity we have employed the following reference basis which we find more satisfactory and accurate.

The following tabulated data are arranged in the same manner as that employed by Dean and Davis, but are based on our own experimental viscosity-temperature measurements of approximately different typical Pennsylvania oils and/or their fractions.

Viscosity (Saybolt seconds) atlfeli* o ay o 100 F' seconds) 210 F. L minus H Series L Series H The rate of change of viscosity with temperature is also measured in terms of a relation shown to exist between Saybolt viscosity and gravity for oils of any particular type (Hill and Coates, Industrial Engineering Chemisty 20.641 (1928)), this relationship being expressed in terms of the viscosity gravity constant calculated from the equation:

A ioor- 1.0752 iugm (v-38)' A=viscositygravity constant G=specic gravity at 60 F.

V=viscosity at 100 F., Saybolt seconds This relation between viscosity and gravity does not vary to any appreciable extent for oils which are produced by distillation from the same crude, but does vary for oils which are produced from diierent base or type crudes. Pennsylvania oils are regarded as being of high quality and for the viscosity-gravity constant give a value of approximately 0.82 whereas naphthenic oils are regarded as being of low quality and give a value of approximately 0.92. L

Since the rate of change in viscosity of oil mixtures with temperature decreases with decrease in percentage of molecules of the first and second classes, it would appear that either the viscosity index or the viscosity-gravity constant is a measure of the viscosity-temperature characteristic of an oil.

However, both methods of measuring the latter characteristic present diiliculties.

For instance, the viscosity index, particularly of light oil fractions, is influenced to a great extent by the accuracy with which the 210 F. viscosity is determined, and also, though to a less extent, by the accuracy with which the 100 F. viscosity is determined.

For example, an error of 1.0 Saybolt second in the 210 F. viscosity determination of a 40.0 second (Saybolt at 210 F.) oil results in an error or" approximately 32 points in the viscosity index of a typical paraiinic oil, and in an error of about 55 points in the viscosity index of a typical naphthenic oil. A similar error in the case of a 45t-second (Saybolt at 210 F.) oil results in an error of about 15 points for a parainic oil and in an error of 27 points for a naphthenic oil.

The inuence of the accuracy of the 100 F. viscosity determination is about one-tenth of that of the 210 F. viscosity determination.

In the case of the heavier oils, the possible error due to inaccurate viscometry methods is somewhat less important but yet must be taken into consideration.

Therefore, it will be seen that very large diferences in viscosity index measurements may result owing to relatively small errors in viscosity measurements, particularly in the case of light oil fractions, making it necessary to exercise a very high degree of skill and care to obtain reasonably correct readings.

A difference of a comparable character does not find its way into viscosity-gravity constant determinations in the case of light oil fractions so that the latter method may be regarded as being somewhat more accurate in the case of light oil fractions.

` However, viscosity-gravity constant determinations require a much greater amount of calculations and this method is, therefore, cumbersome, particularly when investigations are made on a large scale.

Upon an investigation of a representative group of different oils, it is found that a definite relation exists between the viscosity index and the viscosity gravity constant making it possible by a combination of the two to evaluate the viscositytemperature characteristics of an oil by a third and much more uniformly accurate and rapid method than the rst and second methods respectively.

This will be more clearly understood upon reference to the drawing in which Figure 1 is a graph on which the viscosity indexes of the above group of oils are plotted against their viscosity gravity constants.

Figure 2 is a graph on which viscoslties in Sayl mula the numerical value of the viscosity gravity 75.-

. curve is drawn through the plotted points resulting from each chosen value of viscosity index, and

Figure 3 is a graph illustrating the relative value of each unit of difference in viscosity index for oils ranging. from light fractionsl to heavy fractions.

Referring now more particularly to Figure l of the drawing, the curve I0 on graph II shows that the viscosity gravity constant is definitely related to the viscosity index.

This fact indicates and tests have shown that an index number comparable to its viscosity index number (hereinafter referred to for convenience as the gravity index) can be obtained for any mineral oil lubricant of any one type from its viscosity in Saybolt seconds at 100 1'". and its specific gravity at 60F. with a fairly high degree of accuracy.

Furthermore, the nature of curve I0 shows that gravity index numbers may be obtained for Pennsylvania oils (being paraflinic in type) with a high degree of precision.

A form of graph from which the gravity index of a mineral lubricating oil can be obtained accurately is shown at I2 in Figure 2. The curves I3, I4, I5, I6, I1, I8, I9, 20, 2|, 22, 23, 24, and 25 were constructed by connecting all of the points plotted in the manner above indicated for each hypothetical oil. Curves I4, I6, I8, 20, 22, and 24 are shown dotted merely to assist the eye in focusing on any one line.

It is appreciated that the/accuracy of such a graph is dependent to a large extent on its size, but the usual 8.5 by 114 inch plot will result in values which are approximately of the same delgree of accuracy as that which corresponds to an error of 0.10 A. P. I. in gravity. l

To obtain the numerical value of the gravity index for any mineral oil of the type for which graph I2 happens to be constructed whether such oil is extracted or not, it is merely necessary to measure its viscosity at 100 F. in Saybolt seconds, to measure its gravity at 60 "F., and then to plot the values on graph I2 of Figure 2, interpolating the exact value if necessary. Additional curves may be interpolated between those shown if desired to assist in the reading.

This invention is based on the discovery that the gravity index, color and/or Conradson carbon of mineral oils in general and Pennsylvania grade oils in particular may be improved by treating such oils with benzyl acetate.

Oil components in general and particularly those of Pennsylvania grade possess a selective solubility in solvents of the character above set forth in that those components which are largely responsible for a relatively high viscosity change with temperature, for a relatively dark color and/or for a relatively. high Conradson carbon residue are more soluble therein than other oil components not possessing .these characteristics.

Therefore, by an extraction treatment of an 4oil containing both classes of components with the foregoing solvent, it is possible to separate said oil into an oil having a relatively higher viscosity change with temperature, a relatively darker color and/or a relatively higher Conradson carbon residue and an oil having a relatively lower viscosity change with tempera-ture, a relatively lighter color and/or a. relatively lower Conradson carbon residue than that possessed by the original oil.

Furthermore, the solvents herein set forth exhibit a selective solvent power for oxidizable components and for other components which might result in sludge, and for other substances considered deleterious, so that, when the original oil contains one or more of the foregoing, a preponderance thereof will be found in the separated portion of relatively high viscosity change with temperature, of relatively darker color and/or ofrelatively higher Conraclson carbon residue, thereby leaving the separated portion of relatively low viscosity change with temperature, of relatively lighter color and/or of relatively lower Conradson carbon residue in a highly refined state.

In practicing the invention, contact between solvent and oil may be effected by any desired means. be eventually formed, one containing oil components of relatively higher gravity index, of relatively lighter color and/or of relatively lower Conradson carbon residue, and the other solution containing oil components of relatively lower gravity index, of relatively darker color and/or of relatively higher Conradson carbon residue.

This contact may be the result of mechanically mixing the oil witha suitable quantity of one or more of the foregoing solvents, such as by stir- Two immiscible solutions will generally.

ring in a suitable container at any desired suitable temperature to effect either a total or any desired degree of partial solution of solvent and oil. In the event of total solution of the oil and solvent, the mixing may be followed by cooling to cause the formation of twoimmiscible solutions the same as when partial solution only of oil in solvent is originally eiected. This cooling may be in steps so as to cause fractional precipitation. Itis also possible to effect partial solution of oil in solvent at a relatively elevated temperature and then to cool to precipitate a part of the dissolved oil.

Separation of the solutions may be accomplished in any manner, for instance, by allowing the liquid to settle into a two layer system and then decanting, or by centrfuging the liquid.

The solvent may be removed from each ofthe separated solutions by any suitable means, for instance, byf distillation.

The extraction may be repeated on either separated oil portion as many times as desired. The oil might also be treated in a batch countercurrent system wherein the solvent in batches moves countercurrently through a plurality of oil batches, each bath of solvent being separated from each batch of oil before moving on to the next batch of oil.

We nd that continuous countercurrent systems are very suitable.

This is particularly true of certain continuous countercurrent systems which we have developed in which a highly eicient contact between oil and solvent is obtained (with or without precipitation or simulations of reflux) and in which channeling is substantially prevented.

However, any type of apparatus or systems may Extraction of bright stock-Continued the properties of the raffinate of the run. Likewise, the letter E following the run number at the head of a column of gures indicates that thc Flash point, F.. Fire point, F. Pour point, F Percent Conradsou carbon... Color (A. S. T. M. and/or be employed Without departing from the invention Bun number 5R 5E 6R 7R ER The following examples will serve to further illustrate the invention. Solvent-011 volume 5 ratio 17.5:1 1:1 3:1 0:1 Eitracgirn tempera- 122 122 122 Lll Propertzes of Permsylvama lubricating stocks Yield ofmmmteu 84 60 30 used Yield of extract Viscosity at 210 F.- giscostity .512.102)o .1.3.. [BVI y, Blepd of Flash point, F cylinder Fire point, F..... Oil Bright Unlltered Cylinder stock and Pour point. e F

stock neutral stock uni`1l- Percent comadson tered carbon neutral Color (A. s. T. M. 15

and/0r cms.) 5211-814 52.0-81/4 55. 4-8 48.0 Viscosity index 109.5 77.5 100.5 105.0 109.5 Viscosity at 210 F...-. 153 45.15 154. 4 88. 8 Viscosity-gravity Viscosity at F. 2517 182. 6 2370 960 constant 0. 788 0.840 0. 805 0. 798 0. 787 Gravity, A. P. 1.- 25. 9 20. 7 25. 9 27. 5 Gravity index. 118 80 109 112 119 Flash point, F.. 550 420 565 475 gire point, ZF- 620 493 g 5gg our oint. l5 Percelin Conrddsdd o The following runs were made with benzyl 2O carbon.. 1. 728 0, 027 2.178 1.444 com (A. 8 5 23. 6 1) 34. 5 1) acetate `as the solvent and unfiltered neutral viscosinyiddex-.- 97.0 99.0 102.0 100.5 as the oil. viscosity gravity 0 809 0 024 o 810 o 212 stunt Gravityiudex 10G 95 105 104 Extraction of umiltered neutral 25 Run number... QR 10B 11R 12R The following runs were made with benzyl acetate as the solvent and bright stool; as the S01vent.v01umo mom 1:1 3:1 6:1 16:1 on Extraction temperature, F. 32 32 32 32 Yield oi ralinate 88 69 64 20 30 The letter R appearing after the run number mid 0fextrdct. ..12 ..331 330 3 80 iscosity at 210 .5 .8 4 .3 4 .C5 at the head of a column of gures indicates that Viscqsity at 100 F 170.... 156.2 145.0 137.0 the figures of the respective column relate to Gravltinf A. P. I. 3 32.6 33.4

1 1 figures of the column relate to the properties of Vicsssit-y--i 92. oi 90.102 97. (11.?. the extract, Viscosity-gravit 0.814 0. 900 0.893 0. 795 Gravity index 102 107 110 114 Extraction of bright soclc 40 Eastractzofn of unfiltered neutral-Continued Run number 1R 2R 3R 4R 4E Run number 13R 14R 14E 151;

Solvent oi1 volume ratio. 16. 5:1 2:1 5:1 9:1 Extraction temperature Solventjoil volume ratio. F 32 77 77 77 Eritraction temperature Yield 01 meinem-- 05 08 73 58 Yfwld 0f rainate- Yieid di extract... a5 14 27 42 ,leid 9i extract;- Viscosity at 210 F 154. 4 149. 5 152. s 162. 1 154.7 VlSCOSltY at 210 F viscosity at 100 F 2145 2220 2195 2328 3571 VlScQSlWgt 100 F-- Grdv1ry, A. P. i 2s. 5 27.0 27.7 2s. 1 20.9 Gravity.. A.; P. I.. Flash point, F 555 Flash point.; F... Fire point, F.- 525 Fire point, 0F-.. Pour point, F 20 Pour point, F Percent Conradson car- Percent Conradson carbon....

bon 1,005 3.879 Color (A. S.T.M.ziud/or cms.). Color (A. S. T. M. Viscosity indei.: and/o1- cms.)-.-- 50. 2-8 57. 64% 55. 9-8 54. i-y4 VISCOPlty-gwvlty constnt.- Viscosity index 109. o 102. 0 105, 5 1075 72. 5 Gravity index Viscosity-gravity co stage... 0. 789 0. 802 o. 795 0. 729 0. 848 Gravity 1ndex 117 111 114 11d 72 The following runs were made with benzyl ace- Esctractz'om. of cylinder stock .tate as the solvent and cylinder stock as the oil.

Run number IGR 17R 17E IBR Solvent-oil vol. ratio Extraction temp` F. Yield of raiiinate-. Yield of extract Viscosityv at 210 F. Viscosity at F. Viscosity at 100 F. Gravity, A. P. I- Flash point, F Fire point, F

Pour point, F

Percent Conradson carbon Color (A. S. T. M. and/or cms.) Viscosity index Viscosity-gravity constant. Gravity index Note: Asterlsks denote extrapolated vlseosities.

The following runs Were made with benzyl acetate as the solvent and a blend of cylinder stock and unfiltered neutral as the oil.

Etractz'on of blend of cylinder stock: and unfiltered neutral Run number 22R 23R 24R Solvent-oil volume ratio 1 1 6:1 12:1

Extraction temperature F Yield of raffinate Flash point, "F Fire point, F. Pour point, "F.

Percent Conradson carbon 1.010 Color (A. S. T. M. and/or cms.) 33. l-D 29. 1-D NViscosity index lll 114 Viscosity-gravity constan 0A 803 0. 799 Gravity index 111 114 Note: Asterisks denote extrapolated viscosities.

In all of the foregoing runs, contactfbetween solventl and oil was made by single batch methods. Greater eiiiciencies may: be obtained by employ-I ing more efcient methods, for instance, continuous counter-current.

A substance or substances might be added to the solvent to reduce or otherwise modify the -solubility of hydrocarbons therein if desired.

In the foregoing data with respect to color the smaller numerals show the color as measured by A. S. T. M. methods.

The larger numerals, which are referred vto as indicating centimeters, show a relative relationship with 100 centimeters indicating the color of a water-white oil and 0 centimeters an oil sufficiently opaque to cut down the quantity of light transmitted with the light source 0 centimeters away to the same quantity as would pass through the water-white oil with the light source 100 centimeters away.

An increase in centimeters, therefore, indicates improvement in color.

In some cases the products obtained were too dark for determination on this specially constructed colorimeter in the usual manner. In this case the oils were diluted with kerosene. The kerosene used for dilution hada color rating of centimeters. Accordingly all colors reported for these darker products were obtained on kerosense-oil mixtures containing 85% by volume kerosense and 15% by volume oil. The readings so obtained are listed with-the suflix D". The degree of actual improvement in the oils of the above runs will be better appreciated upon reference to Figure 3 wherein is shown a graph 26 having curves 21, 28; 29, 30, 3l, 32 and 33. Curve 21 was constructed by plotting the viscosity indexes of a series of hypothetical oils against their viscosities in Saybolt' seconds at 210 F. Each of the series of hypothetical oils was assumed to have no'viscosity difference between F. and 210 F. The curve 21, therefore, represents thev maximum improvement that can be hoped for as far as the viscosity-temperatur characteristics of an oil is concerned.

It will be noted that the curve 21 slopes downwardly toward the right, the slopes at the various points on the curve 21 beingquite extreme at the left and becoming less extreme at the right, but there is nevertheless, a decided downward tendency. lThis is due to the manner in which the viscosity index was originally developed and clearly shows that a difference of one point in the viscosity index of an oil of, for instance, 280 seconds viscosity at 210 F. is of as much importance as a difference of about 3.5 points in the viscosity index of an oil having a viscosity of, for instance, 40 seconds at 210 F.

'The curves 21 to 33 inclusive have'been interpolated to represent different percentages of improvement in viscosity index over that normally possessed by a Pennsylvania grade oil. Base line 34 is given a Value of 100 since Pennsylvania oils are rated at 100 in viscosity index. Curve 33 represents an improvement of 10%; curve 32, 20%; curve 3l, 30%; curve 30, 40%; curve 29, 60%; and curve 28, 80%.

From the foregoing it will be seen that a mineral oil and particularly one of Pennsylvania. grade may be divided into any desired number of portions having different gravity indexes, having different color ratings and/or having different Conradson carbon residue ratings and may be simultaneously otherwise refined.

Since it is much more difficult to improve a petroleum oil of Pennsylvania grade due to its original high quality and since such oils may be very substantially improved by the process herein, it follows thatthe process will eiTect very substantial improvements in other oils such as those of naphthenic and/or asphaltic characteristics.

In the claims, the term lubricating oil when referred to is intended to mean an oil of a viscous character, that is, of the order of 40 Saybolt seconds at 210 F. or above.

While procedure for the purpose of carrying out the invention has been particularly described, it is to be understood that this is by way of illustration, and that changes, omissions, additions, substitutions, and/or modifications may be made without departing from the spirit of the invention which is intended to be limited only as required by the prior art.

We claim:

1. A process comprising contacting a mineral oil containing components of different characteristics with benzyl acetate under conditions causing the formation of two phases to produceportions of said o il respectively` exhibiting certain of said characteristics to a greater' and to a less A mation of two phases to produce portions of said oil respectively of lighter and darker color.

4. A process comprising contacting a mineral oil containing components responsible for Conradson carbon residue with benzyl acetate under conditions causing the .formation of two phases to produce portions of said oil respectively of higher and lower concentrations of said components.

5. A process comprising contacting a petroleum ol of Pennsylvania grade containing components of diiferent characteristicswith benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively exhibiting certain of said characteristics to a greater and to a less degree. y

6. A process comprising contacting a petroleum oil of Pennsylvania grade containing components oi different gravity index with benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively of higher and lower gravity index.

7. A process comprising contacting a petroleum oil of Pennsylvania grade containing components of different color with benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively of lighter and darker color.

8. A process comprising contacting a petroleum oil of Pennsylvania grade containing components responsible for Conradson carbon residue with benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively of higher and lower concentrations of said components.

9.' A process comprising contacting a lubricating oil of Pennsylvania grade containing components of different characteristics with a benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively exhibiting certain of said characteris tics to a greater and to a less degree.

l0. A process comprising contacting a lubricating oil of Pennsylvania grade with benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively of higher and lower gravity index.

1l. A process comprising contacting a lubricatlng oil of Pennsylvania grade with benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively of darker and lighter color.

l2. A process comprising contacting a lubricating oil of Pennsylvania grade with benzyl acetate under conditions causing the formation of two phases to produce portions of said oil respectively of higher and lower concentrations rin components responsible for Conradson carbon residue.

13. A process comprising contacting a petroleum oil with benzyl acetate under conditions conducive to the formation of two liquid phases, and separating said phases to produce oil portions of higher and lower gravity index, said petroleum oil being of a character such that the ranate portion will have a viscosity index above 100. .I

14. A process comprising contacting a lubricating oil fraction of Pennsylvania grade with benzyl acetate under conditions conducive to the formation of two liquid phases, separating said phases, said original oil fraction being of a character such that the raiinate produced will have a viscosity at 210 F. at least substantially as high as the viscosity at 210 F. of the original oil.

15. A lubricating oil having a viscosity gravity constant at least as low as 0.80 and resulting from the solvent treatment of a lubricating oil of Pennsylvania grade with benzyl acetate.

MERRELL R. FENSKE. WILBERT B. MCCLUER. 

